Multistage pump assembly

ABSTRACT

A modular pump assembly has a volute ( 16 ), having a suction chamber ( 120 ) and a pressure chamber ( 122 ), and a pump stack ( 14 ) having at least one stage ( 86 ), wherein a modular flange ( 44 ) is arranged between the volute ( 16 ) and the pump stack ( 14 ) and is removably coupled to both the pump stack ( 14 ) and the volute ( 16 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Section 371 of International Application No. PCT/EP2007/008779, filed Oct. 9, 2007, which was published in the English language on Apr. 17, 2008, under International Publication No. WO 2008/043527 A1, which claims the benefit of U.S. Provisional Application No. 60/850,871, filed Oct. 10, 2006, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates generally to pump assemblies, and more particularly, to multistage end-suction pump assemblies.

Pump assemblies are provided within pipe systems of residential, commercial or industrial facilities for increasing the pressure and flow of the fluid within the pipe system. The pump assembly is usually fitted to the pipe system to circulate the fluid under pressure. The typical pump assembly has an inlet that supplies fluid to the pump through a manifold having an impeller chamber, an impeller located in the chamber, a power head (e.g., motor and shaft) to drive the impeller, and an outlet that returns the fluid to the pipe system. The inlet is fitted to a supply pipe and the outlet is fitted to a discharge pipe. The size of the pump assembly is selected based on the particular pipe system and the desired pressure and flow of the fluid within the pipe system. For example, various pump assembly components may be provided to accommodate various sized supply pipes and discharge pipes, which are typically different from one another. The particular pump assembly components chosen depend on the particular application. In another example, in applications where a high pressure is desired, a pump assembly having a relatively larger motor or a relatively larger impeller may be used. In some known pump assemblies, multiple impellers are used, such as in a multistage pump assembly.

The multistage pump assemblies typically have one of two configurations, namely a horizontal configuration and a vertical configuration. In both configurations, the pump assemblies typically stack the multiple impellers in stages in series. In the horizontal configuration, the stack is oriented generally horizontally when installed; and in the vertical configuration, the stack is oriented generally vertically when installed.

In the typical horizontal configuration a volute or manifold is provided at one end of the pump stack and including inlet and outlet of the pump. On the opposite end of the pump stack the drive motor is connected with the pump stack.

Since, as described above, size and type of the pump stack may vary depending on the use of pump, it is necessary to provide different manifolds or volutes which are designed to be connected to a certain pump stack, for example depending on the diameter of the pump stack. Further, the design of the manifold or volute depends on the required design of inlet and outlet so that the inlet and outlet can be connected with an existing pipe system. For example, inlet and outlet may be arranged in line or angled, for example at 90° to one another. Further, the diameter of inlet and outlet and also the length of inlet and outlet may be designed depending on the pipe system into which the pump has to be integrated. Therefore, many different types of manifolds or volutes are required for the different types of pump stacks and different installations for the pump assembly.

BRIEF SUMMARY OF THE INVENTION

In view of this it is the object of the invention to provide an improved modular multistage pump assembly which allows a universal use for different pipe systems and with different sized pump stacks and avoids providing many different types of manifolds or volutes to connect the pump stack with the pipe system.

According to the invention, a modular multistage pump assembly is provided including a volute having a suction side and a pressure side, a pump stack having at least one stage, and a modular flange coupled to each of the volute and the pump stack.

The volute or manifold comprises a suction chamber and a pressure chamber and is connected with the pump stack having at least one stage, but preferably comprising more than one stage. According to the invention the volute and the pump stack are not directly coupled with each other, but by a modular flange arranged between the volute and the pump stack. The modular flange is removably coupled to both the pump stack and the volute. Thus, the modular flange is a connection element providing the connection of the volute and the pump stack. By this arrangement the modular flange may serve as an adapter to connect different pump stacks with the same volute or different volutes with the same pump stack. By use of the modular flange it is not necessary to specially adapt the volute to a certain pump stack design or to design the pump stack corresponding to the design of a certain volute. It is sufficient to just provide several modular flanges of different design which can be used to couple the different volutes or pump stacks with each other. The number of different volutes necessary to couple different pump stacks with different pipe systems can thereby be reduced, since the necessary number of volutes depends only on the design of the pipe system to which the pump shall be coupled. For connecting the volute with different types or sizes of pump stacks, the adapter in a form of the modular flange is used. It is much easier to provide different modular flanges than different volutes, so that the costs for the different pump designs can be reduced. This will give the benefit of less inventory and increased on-time delivery to the customer.

Preferably the modular flange has two surfaces opposite to one another, wherein the first surface is designed corresponding to a connection surface of the volute or manifold and the second surface is designed corresponding to a connection surface of the pump stack. This means that the first surface of the modular flange is adapted to the design of the interface of the volute for connection with the pump stack. The opposite surface of the modular flange is designed corresponding to the interconnection elements or surface of the pump stack.

Further, it is preferred that the modular flange be exchangeable in such a way that different volutes and pump stacks may be connected with one another by use of a corresponding modular flange. This means that different modular flanges may be provided for connection of different volutes and pump stacks and in particular different pump stacks with the same volute.

Thus, by the different modular flanges different adapters for connecting volute and pump stack are provided.

According to a preferred embodiment, the pump stack and/or the volute comprises at least a first and a second type, and the modular flange is configured to be coupled to each of the first type and the second type. By such design the number of different modular flanges required is reduced, since one modular flange may be coupled with different volutes and/or pump stacks. For example, the modular flange may have two sets of connection elements, such as screw holes, for connecting the modular flange with two different types of pump stacks or with two different types of volutes.

In a similar way, it may be preferred that the pump stack and/or the volute comprise at least a first and a second size and that the modular flange be configured to be coupled to each of the first size and the second size. This means that the same modular flange may be coupled, for example, with two different sized pump stacks or with two different sized volutes. By this arrangement the number of necessary modular flanges necessary for connecting all types and sizes of volutes and pump stacks with one another is reduced.

Further, it is preferred that the modular flange define a suction chamber and a pressure chamber. The suction chamber of the modular flange is connected with the suction chamber of the volute, and the pressure chamber of the modular flange is in connection with the pressure chamber of the volute. Thus, the suction chamber of the volute can be connected with the suction channel of the pump stack by the suction chamber of the modular flange. In the same way, the pressure chamber of the volute can be connected with the pressure channel of the pump stack by the pressure chamber in the modular flange.

Further, it is preferred that the modular flange connecting the pump stack and the volute include concentric rings defining a radial inner channel in direct fluid communication with the suction chamber of the volute and a radial outer channel in direct fluid communication with a pressure chamber of the volute. Thus, the radial inner channel is the suction chamber of the modular flange, and the radial outer channel is the pressure chamber of the modular flange. The inner channel and the outer channel may be separated from one another by a cylindrical wall which is connected with the radial outer part of the modular flange by one or more ribs, preferably extending in a radial direction.

Further, it is preferred that the pump stack include at least two stages of diffusers abutting one another and defining an axially extending inner tube and an axially extending sleeve being radially spaced outwardly with respect to the inner tube, wherein the inner tube defining a suction channel along the inner portion of the tube and the inner tube and the sleeve defining a pressure channel therebetween, the suction channel being in fluid communication with the inner channel of the modular flange and the pressure channel being in fluid communication with the outer channel of the modular flange. Preferably, the modular flange has a ring-shaped or cylindrical wall having substantially the same diameter as the inner tube of the pump stack, so that the axial end of the inner tube of the pump stack and the cylindrical wall of the modular flange may come in contact with one another, so that a suction channel extending through the inner part of the modular flange and the inner part of the pump stack is formed. At the same time, a ring-shaped outer pressure channel surrounding the inner tube of the pump stack and cylindrical wall of the modular flange is formed.

According to a further preferred embodiment, the modular flange comprises at least one set of fastening elements for coupling with the pump stack and at least one set of fastening elements for coupling with the volute. The fastening elements of the modular flange are arranged and designed so that they can be connected with corresponding fastening elements of at least one volute and at least one pump stack.

Preferably, the fastening elements for coupling with the pump stack and/or the fastening elements for coupling with the volutes comprise a set of holes in the modular flange. These holes can be used to introduce screws or bolts for connecting the modular flange with the volute and/or with the pump stack.

Further, it is preferred that at least one seal is provided between the modular flange and the volute and/or between the modular flange and the pump stack. Such seals are used to form fluid channels extending from the volute through the modular flange to the pump stack, which are fluid tight to one another and to the outside.

According to a further preferred embodiment, the volute comprises an inlet connected to the suction chamber and an outlet connected to the pressure chamber of the volute. The inlet and the outlet are used for connection with a pipe system.

Preferably, the volute comprises an inlet fitting and/or an outlet fitting removably coupled to the inlet and outlet, respectively. These fittings may be used to connect the same volute with different pipe systems. For example, the fittings may have different lengths, so that the pump assembly can easily be introduced in an existing pipe system in which the pipe ends for connecting with the pump assembly are already located at predefined positions. Thus, the fittings serve as adapters for connecting one volute with different pipe systems. Further, it may be possible to provide fittings having different sized connection ends for connecting with the surrounding pipe system, so that it is possible to easily connect the volute with different sized pipes. By providing these fittings on the volute the number of required volutes may be reduced, since for different installations only the fittings may be changed, but not the entire volute.

Thus, preferably the inlet fitting and/or the outlet fitting is exchangeable in such a way that fittings of different size and/or type can be coupled with the volute to enable the integration of the pump assembly into different pipe systems.

Further, the invention refers to a system for assembling a modular pump assembly according to the preceding description. This system comprises at least two different pump stacks and/or at least two different volutes and at least two different modular flanges. These at least two modular flanges are configured such that they allow the coupling of the different pump stacks with the different volutes. It is preferred to provide so many different modular flanges, that each desired combination of a pump stack and a volute can be achieved by using a special modular flange for connecting both.

Preferably, a multistage end-suction pump assembly is provided including a pump stack extending between a volute end and a head end, wherein the pump stack includes at least one stage of impellers aligned to rotate about a rotation axis. The pump assembly also includes a volute coupled to the volute end of the pump stack, wherein the volute includes an inlet and an outlet being oriented non-parallel with respect to one another.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:

FIG. 1 is side perspective view of a pump assembly formed in accordance with an exemplary embodiment of the invention.

FIG. 2 is an exploded view of the pump assembly shown in FIG. 1.

FIG. 3 is a partial cutaway view of the pump assembly shown in FIG. 2.

FIG. 4 is a side perspective view of an alternative sleeve flange for the pump assembly shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a side perspective view of a pump assembly 10 formed in accordance with an exemplary embodiment. The pump assembly 10 includes a pump motor 12, a multistage pump stack 14 and a manifold or volute 16. The pump assembly 10 may be installed in an existing or new pipe system to a supply pipe and a discharge pipe (not shown) for increasing the pressure and/or flow of water or another fluid within the pipe system. In the illustrated embodiment, the pump assembly 10 represents a horizontal pump assembly that may be mounted to a base 18 via a plurality of supports or braces, such as motor supports 20, a pump stack support 22, and volute supports 24. The base 18 is generally planar and is oriented horizontally, and may be mounted, directly or indirectly to a ground or building surface (not shown). While various embodiments of horizontal pump assemblies are described below, it is understood that the pump assembly 10 may be beneficial in other, non-horizontal applications as well. The following embodiments are therefore provided for illustrative purposes only.

FIG. 2 is an exploded view of the pump assembly 10, illustrating the motor 12, the pump stack 14 and the volute 16 being axially aligned with one another along a longitudinal or rotation axis 30. The motor 12 includes a motor shaft 32 aligned with the rotation axis 30, and the pump stack 14 includes a pump shaft 34 aligned with the rotation axis 30. The motor shaft 32 and the pump shaft 34 are interconnected by a shaft coupling 36 for transferring rotational movement from the motor shaft 32 to the pump shaft 34. The shaft coupling 36 is housed within an enclosure 38 extending between the motor 12 and the pump stack 14. The pump stack 14 includes a pump head 40 and a sleeve 42 extending from the pump head 40 to a sleeve flange 44 opposite the pump head 40. The sleeve 42 has a generally circular cross section and defines a chamber through which the fluid flows. In the illustrated embodiment, and as will be explained in greater detail below, the pump stack 14 includes an inner channel or chamber and an outer channel or chamber through which the fluid is channeled. The sleeve 42 defines a radially outer surface of the outer chamber. The sleeve flange 44 is separately provided from, and coupled to, the sleeve 42. The sleeve flange 44 is retained in place with respect to the sleeve 42 and the pump head 40 by multiple staybolts 46 extending between the pump head 40 and the sleeve flange 44. The pump shaft 34 extends through the pump stack 14 and is substantially centered within the chamber defined by the sleeve 42. Optionally, an end of the pump shaft 34 may be supported by a bearing support 48 integrated with the sleeve flange 44.

The sleeve flange 44 forms a modular flange serving as an adapter for coupling different pump stacks and volutes with one another. The sleeve flange 44 on one side is designed or configured to be connected with the pump stack in particular with the sleeve 42, the impeller assemblies 86 (see FIG. 3) and the staybolts 46. On the other side the sleeve flange 44 is configured to be coupled with the rear end 52 of the volute 16. In case a different sized or different configured pump stack 14 should be connected with the same volute 16, just a different sleeve flange 44 can be used to couple the pump stack 14 with the same volute 16. This different sleeve flange 44 has a different design for connection with the different pump stack 14, but on the other side the same configuration or design for connecting with the rear end 52 of the volute 16. In case there is provided a certain number of different sized or designed pump stacks 14 and a certain number of different designed volutes 16, it is preferred to provide such a number of different modular flanges or sleeve flanges 44 that any required combination of a pump stack 14 and a volute 16 can be realized by just taking the corresponding sleeve flange 44 to couple the pump stack 14 and the volute 16 of the desired combination with one another.

The volute 16 includes a front end 50, a rear end 52, a top 54, a bottom 56, and sides 58 and 60. The volute supports 24 may be coupled to the sides 58, 60 using known fasteners or known fastening methods. The volute 16 is coupled to the sleeve flange 44 via a volute flange 62 extending radially outwardly at the rear end 52 of the volute 16, such as using known fasteners and known fastening methods. The volute 16 is coupled to the sleeve flange 44, such that the volute 16 is in fluid communication with the pump stack 14.

In the illustrated embodiment, the volute 16 represents an end-suction volute having an inlet 64 at the front end 50 and an outlet 66 at the top 54. The inlet 64 and the outlet 66 are non-parallel with respect to one another, such that the volute 16 has a non-in-line configuration (e.g., an orientation in which the inlet and the outlet are not aligned with one another along an axis). Optionally, the inlet 64 and the outlet 66 may be generally perpendicular with respect to one another, such as the end-suction, 90 degree discharge configuration illustrated in FIG. 2. Optionally, the inlet 64 is oriented in-line with the rotation axis 30, such that the fluid flows through the inlet 64, the volute 16, the sleeve flange 44 and the pump stack 14 in a direction along the rotation axis 30, shown by the arrow A. Other configurations and orientations of the inlet and outlet 64 and 66 are contemplated in alternative embodiments, such as on the front end 50, top 54, bottom 56 or sides 58, 60 in a non-in-line configuration.

In the illustrated embodiment, the volute 16 includes an inlet fitting 68 and an outlet fitting 70 coupled to the inlet 64 and outlet 66, respectively. The fittings 68, 70 are separately provided from the volute 16 and mountable thereto. Thus, the fittings 68, 70 can be used as adapters to connect the volute 16 with pipe systems of different configuration and size. The fittings 68, 70 may be securely coupled to the volute 16 using known fasteners or fastening methods. For example, the fittings 68, 70 may be threadably coupled to the volute 16; the fittings 68, 70 may be coupled to the volute 16 using a integral flanges and corresponding fasteners; the fittings 68, 70 may be soldered or welded to the volute 16; and the like. The fittings 68, 70 are also configured for attachment to the supply and discharge pipes, respectively, such as by a flange coupling, a threaded coupling, a soldered coupling, and the like. The type and size of fitting 68, 70 (e.g., flange, threaded, and the like) may be selected based on the type of mating fitting included on the supply and discharge pipes. A modular volute 16 is thus provided that may be adapted for installation to an existing piping system. Optionally, the types of fittings 68, 70 may be the same and/or the size of the opening of the fittings 68, 70 may be the same. Alternatively, the type and/or size of the fittings 68, 70 may be different from one another. In the illustrated embodiment, the outlet fitting 70 constitutes a modular discharge spool having first and second flanges at the ends thereof. Multiple discharge spools may be provided with the pump assembly 10, wherein each spool has different dimensions, such as opening size, flange size, height, width, length, thickness, fitting type, and the like. The discharge spools are interchangeable with the volute 16 to accommodate a range of discharge pipe configurations. In the illustrated embodiment, the inlet fitting 68 constitutes a connection using a snap ring 72 and corresponding grooves on each of the inlet fitting 68 and the volute 16 at the inlet 64 (victaulic connection). The inlet fitting 68 also includes a flange for interconnection with the supply pipe. However, other types of interconnection may be accomplished in lieu of the flange coupling. Optionally, multiple fittings may be provided with the pump assembly 10, wherein each fitting has different dimensions, such as opening size, flange size, height, width, length, thickness, fitting type, and the like. The multiple fittings are interchangeable with the volute 16 to accommodate a range of supply pipe configurations. In alternative embodiments, other connecting methods and devices may be employed, such as a threaded coupling, a welded or soldered coupling, and the like. Optionally, seals may be positioned between the fittings 68, 70 and the volute 16 to seal the interconnection therebetween. In alternative embodiments, the fittings 68, 70 may be integrally formed with the volute 16 and positioned for interconnection with the supply and discharge pipes.

FIG. 3 is an exploded, partial cutaway view of the pump assembly 10 illustrating the pump head 40, the sleeve 42, the sleeve flange 44 and the volute 16 being cutaway. As illustrated in FIG. 3, the pump stack 14 includes a seal cartridge 80 located between the pump head 40 and the pump shaft 34. The seal cartridge 80 seals against fluid leakage from the pump stack 14 at the pump head 40. The pump shaft 34 is rotatable within the seal cartridge 80, and the seal cartridge 80 operates to seal the fluid from escaping from the pump stack 14.

The pump stack 14 extends from a first end 82 to a second end 84 and includes multiple stages of impeller assemblies 86 between the first and second ends 82, 84. Any number of stages may be provided depending on the particular application and the desired flow rate or pressure of the pump assembly 10. The first end 82 is located proximate the volute 16, and in the exemplary embodiment, the sleeve flange 44 is coupled to the first end 82. The second end 84 is located proximate the pump head 40, and in the exemplary embodiment, the pump head 40 defines the second end 84. The impeller assemblies 86 each include an impeller (not shown) therein that is coupled to the pump shaft 34. The impeller rotates to channel the fluid through the corresponding stage. Each impeller assembly 86 includes a diffuser 87 shaped to force the fluid from an upstream stage to a downstream stage as the fluid is pumped from the first end 82 to the second end 84. Each stage includes a single impeller and a single diffuser 87. Additionally, the first impeller assembly 86 includes a diffuser represented by suction interconnector 89 at the upstream end of the first stage. The suction interconnector 89 is sized to interconnect the sleeve flange 44 and the downstream diffusers 87. In the illustrated embodiment, the suction interconnector 89 includes a necked down portion having a reduced diameter at the end thereof for joining with the sleeve flange 44. Optionally, at least one of the stages may constitute a bearing stage that includes a bearing for supporting the pump shaft 34. Such bearing stages are used more often in longer pump stacks 14.

The impeller assemblies 86 include an outer surface 88 spaced radially outward from the pump shaft 34 and spaced radially inward from the sleeve 42. A suction, or radially inward, channel or chamber 90 is positioned between the outer surface 88 of the impeller assemblies 86 and the pump shaft 34. The impellers are positioned within the suction chamber 90. A discharge, or radially outward, channel or chamber 92 is positioned between the outer surface 88 of the impeller assemblies 86 and the sleeve 42. The suction and discharge chambers 90, 92 are axially aligned, but radially split or spaced with respect to one another. The suction chamber 90 is in fluid communication with, and extends between the inlet 64 of the volute 16 and the discharge chamber 92, and the pressure or discharge chamber 92 is in fluid communication with, and extends between the suction chamber 90 and the outlet 66 of the volute 16.

As described above, the sleeve flange 44 is located at the first end 82 of the pump stack 14. The sleeve flange 44 includes an outer surface 94, from which a flange portion 96 of the sleeve flange 44 extends. The volute flange 62 is coupled to the flange portion 96 during assembly of the pump assembly 10. The outer surface 94 has a substantially circular cross section and is sized substantially the same as the sleeve 42. Optionally, the outer surface 94 defines an extension of the sleeve 42 wherein an end of the outer surface 94 abuts the first end 82 of the sleeve 42 and continues upstream from the sleeve 42. Alternatively, the outer surface 94 may be slightly larger than the sleeve 42, such that the sleeve 42 may fit within the outer surface 94 in sealing engagement. Optionally, a seal (not shown) may be positioned between the outer surface 94 and the sleeve 42 for sealing the connection therebetween. The seal and/or the sleeve 42 may be received within an annular groove 98 in the outer surface 96. Optionally, the annular groove 98 is positioned at a rear end of the sleeve flange 44.

The sleeve flange 44 further includes a concentric ring 100 positioned radially inward with respect to the outer surface 94. The concentric ring 100 forms a cylindrical wall and is positioned to separate water flowing within the suction chamber 90 from water flowing within the discharge chamber 92. Optionally, the concentric ring 100 operates as an extension of the outer surface 88 of the impeller assemblies 86. The concentric ring 100 is supported and positioned by ribs or braces 102 extending between the concentric ring 100 and the outer surface 96.

Optionally, the sleeve flange 44 may include a bearing support 104 at a central portion of the sleeve flange 44. The bearing support 104 includes a mating bearing 106 that engages with a corresponding mating bearing 108 of the pump shaft 34. The bearing support 104 operates to support the mating bearings 106, 108 and the pump shaft 34. The bearing support 104 is supported by braces 110 extending between the concentric ring 100 and the bearing support 104.

The volute 16 includes an inner chamber 120 and an outer chamber 122. The inner chamber 120 is the suction chamber and the outer chamber 122 the pressure chamber of the volute. The inner chamber 120 is in fluid communication with the inlet 64 and the outer chamber 122 is in fluid communication with the outlet 66. The inner chamber 120 extends between the inlet and the concentric ring 100 of the sleeve flange 44, and restricts fluid flow directly between the inlet 64 and the outlet 66. In the illustrated embodiment, the inner chamber 120 is axially aligned with the inlet 64 and the suction chamber 90 of the pump stack 14 and extends axially along the rotation axis 30. The inner chamber 120 channels all of the fluid entering the inlet 64 to the suction chamber 90 via the sleeve flange 44. Optionally, the inner chamber 120 includes a transition section 124 that changes size from the upstream end to the downstream end. In the illustrated embodiment, the transition section 124 increases in diameter from the upstream end to the downstream end. The diameter of the inner chamber 120 is substantially equal to the diameter of the concentric ring 100. Optionally, registers 126 and 128 are provided on each of the concentric ring 100 and the volute 16 at the rear end 52 where the volute 16 is joined to the sleeve flange 44.

The outer chamber 122 extends between the front end 50 and the rear end 52 of the volute 16. The outer chamber 122 is positioned radially outwardly with respect to the inner chamber 120, and completely surrounds the inner chamber 120. The outer chamber 122 is axially aligned with the outer chamber 92 of the pump stack 14 and receives fluid therefrom and directs the fluid to the outlet 66.

In the embodiment of FIG. 3, the volute support 24 is represented by a bottom support at the bottom 56 of the volute 16.

FIG. 4 is a side perspective view of a modular flange or sleeve flange 200 for the pump assembly 10 and formed in accordance with an alternative embodiment. The sleeve flange 200 includes an outer surface 202, from which a flange portion 204 of the sleeve flange 44 extends. The outer surface 202 is dimensioned to interface with the sleeve 42 and the volute 16 (both shown in FIG. 3) in a similar manner as the sleeve flange 44 described above. The sleeve flange 200 further includes a concentric ring 206 positioned radially inwardly with respect to the outer surface 202. The concentric ring 206 forms a cylindrical wall and is dimensioned and positioned to interface with the sleeve 42 and the volute 16 in a similar manner as the sleeve flange 44 described above. The concentric ring 206 is supported and positioned by ribs and braces 208 extending between the concentric ring 206 and the outer surface 202. The sleeve flange 200 does not include a bearing support. The sleeve flange 200 is open radially inwardly from the concentric ring 206 and fluid is able to flow unobstructed therethrough.

An exemplary operation of the pump assembly 10 will be described below with reference to FIGS. 1-3. In operation, water or another fluid enters the volute 16 at the inlet 64 via the inlet fitting 68 from the supply pipe. In the illustrated embodiment, the fluid flows axially through the inlet 64 and through the volute 16 to the pump stack 14. Between the inlet 62 and the outlet 64, the fluid is pumped through the multistage pump stack 14, wherein the pressure of the fluid is increased based on the number of stages within the pump stack 14. Within the pump stack 14, the fluid initially passes through the suction interconnector 89 of the first, or upstream, stage of the pump stack 14. The suction interconnector 89 defines the upstream end of the suction chamber 90. The fluid is channeled by the suction interconnector 89 and/or the diffuser 87 into a bottom runner or impeller of the first pump stage, and the impeller forces the fluid to the diffuser 87 of the first stage. The diffuser 87 of the first stage channels the fluid into the impeller of the second stage. Correspondingly, a plurality of stages may be arranged one after another depending on the pressure differential required. For example, any number of pump stages may be selected depending on the particular outlet fluid requirements, such as flow, pressure, and the like, and sleeves 42 of various lengths may be provided to accommodate the chosen number of pump stages. The staybolts 46 may also be sized accordingly. Optionally, the pump assembly 10 may include a single stage.

Once the fluid is forced through the last pump stage, the fluid is conveyed to the discharge chamber 92. The fluid is channeled through the discharge chamber 92 to the outer chamber 122 of the volute 16. The outer surface 88 of the impeller assemblies 86 separates and isolates the inner and outer chambers 90, 92. Similarly, the concentric ring 100 separates or isolates the fluid flowing between the inner chambers 90, 120 from the fluid flowing between the outer chambers 92, 122. The fluid within the annular space of the outer chamber 122 of the volute 16 is expelled from the volute 16 through the outlet 66 and into the discharge pipe.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims. 

1.-15. (canceled)
 16. A modular multistage pump assembly comprising a volute (16), the volute having a suction chamber (120) and a pressure chamber (122), and a pump stack (14) having at least one stage (86), wherein a modular flange (44) is arranged between the volute (16) and the pump stack (14) and is removably coupled to both the pump stack (14) and the volute (16).
 17. The modular multistage pump assembly according to claim 16, wherein the modular flange (44) has first and second surfaces opposite to one another, wherein the first surface is designed corresponding to a connection surface (52) of the volute (16) and the second surface is designed corresponding to a connection surface of the pump stack (14).
 18. The modular multistage pump assembly according to claim 16, wherein the modular flange (44) is exchangeable in such a way that different volutes (16) and different pump stacks (14) may be connected with one another by use of a corresponding modular flange (44).
 19. The modular multistage pump assembly according to claim 16, wherein the pump stack (14) and/or the volute (16) comprise at least a first and a second type and that the modular flange (44) is configured to be coupled to each of the first type and the second type.
 20. The modular multistage pump assembly according to claim 16, wherein the pump stack (14) and/or the volute (16) comprise at least a first and a second size and that the modular flange (44) is configured to be coupled to each of the first size and the second size.
 21. The modular multistage pump assembly according to claim 16, wherein the modular flange (44) defines a suction chamber and a pressure chamber.
 22. The modular multistage pump assembly according to claim 21, wherein the modular flange (44) connecting the pump stack (14) and the volute (16) includes concentric rings (100) defining a radial inner channel in direct fluid communication with the suction chamber (120) of the volute (16) and a radial outer channel in direct fluid communication with the pressure chamber (122) of the volute (16).
 23. The modular multistage pump assembly according to claim 22, wherein the pump stack (14) includes at least two stages (86) of diffusers abutting one another and defining an axially extending inner tube, and an axially extending sleeve (42) being radially spaced outwardly with respect to the inner tube, the inner tube defining a suction channel (90) along the inner portion of the tube, and the inner tube and the sleeve (42) defining a pressure channel (92) therebetween, the suction channel (90) being in fluid communication with the inner channel of the modular flange (44) and the pressure channel (92) being in fluid communication with the outer channel of the modular flange (44).
 24. The modular multistage pump assembly according to claim 16, wherein the modular flange (44) comprises a least a first set of fastening elements for coupling with the pump stack (14) and at least second set of fastening elements for coupling with the volute (16).
 25. The modular multistage pump assembly according to claim 22, wherein the first set of fastening elements for coupling with the pump stack (14) and/or the second set of fastening elements for coupling with the volute (16) comprises a set of holes in the modular flange.
 26. The modular multistage pump assembly according to claim 16, wherein at least one seal is provided between the modular flange (44) and the volute (16) and/or between the modular flange (44) and the pump stack (14).
 27. The modular multistage pump assembly according to claim 16, wherein the volute (16) comprises an inlet (64) connected to the suction chamber (120) and an outlet (66) connected to the pressure chamber (122).
 28. The modular multistage pump assembly according to claim 27, wherein the volute(16) comprises an inlet fitting (68) and/or an outlet fitting (70) removably coupled to the inlet (64) and outlet (66), respectively.
 29. The modular multistage pump assembly according to claim 28, wherein the inlet fitting (68) and/or the outlet fitting (70) is exchangeable in such a way that fittings (68, 70) of different size are couplable with the volute (16) to enable integration of the pump assembly into different pipe systems.
 30. A system for assembling the modular pump assembly according to claim 16, comprising at least two different pump stacks (14) and/or at least two different volutes (16) and at least two different modular flanges (44), wherein the modular flanges (44) are configured to allow coupling of the different pump stacks (14) with the different volutes (16). 